Almost All Women With Breast Cancer Are Also Vitamin D Deficient

We all know someone who's been affected by breast cancer, so it shouldn't come as a surprise that it's the most common type of cancer worldwide. According to a 2022 review published in The Breast, breast cancer accounts for one in eight cancer diagnoses and resulted in a total of 2.3 million new cases in 2020. 

As common as this devastating cancer is, there's very little attention paid to its link to vitamin D status. And yet, up to 96%1 of the breast cancer population is also deficient in vitamin D, per a 2017 review published in Breast Cancer. 

While research on the exact mechanisms and pathways of the sunshine vitamin's effect on breast cancer are ongoing, evidence consistently shows a clear association between circulating vitamin D [i.e., 25(OH)D serum vitamin D levels] and breast cancer risk.

In a 2015 case-control study from Breast Cancer Research and Treatment, women deficient in vitamin D [i.e., with 25(OH)D levels below 20 ng/ml] had a 27% higher risk5 of breast cancer than women with sufficient vitamin D levels. But while clinical vitamin D sufficiency is defined as 25(OH)D levels above 30 ng/ml, other research indicates that higher levels provide greater protection against breast cancer risk.

Evidence suggests the average person needs to consume 5,000 IU of vitamin D3 per day to reach the goal serum level of 50 ng/ml. The problem? Food sources high in vitamin D don't offer enough to help you achieve this goal (unless you're drinking 50 glasses of milk a day, that is). 

And though it's nicknamed the "sunshine vitamin," most people don't get enough safe sun exposure to achieve optimal vitamin D status. Age, latitude, skin tone, season, climate, skin tone, and biological sex all impact one's ability to produce vitamin D from sun exposure, so it's not a reliable source for most.

A whopping 96% of the breast cancer population is also deficient in vitamin D. Science shows that achieving vitamin D sufficiency (specifically, serum levels of 47 ng/ml or higher) can help cut your breast cancer risk in half.